Aha! So I found out from the same Lego Representative after he did some investigating. “Looks like that part 98613 is a singular component that is not found by itself and will always have a black rubber insert. Together, they both make up element 74261 which is a combination of both pieces. That is how it would be found in sets. The outer shell is made of HV-PC and the inside ball joint is made of TPU, or thermoplastic polyurethane. It is not rubber, but a different type of plastic.” So the black part is made of TPU but I’m not sure how long it lasts, I can’t find any information on longevity online.
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